Intraluminal stent and graft

ABSTRACT

An intraluminal stent and graft includes a stent made of a continuous helix of zig-zag wire and loops which connect adjacent apices of the wire. The stent is compressible and self-expandable substantially to a pre-compressed configuration. The device also includes a graft secured to the stent and made of a suitable biocompatible material.

[0001] This application is a continuation of U.S. application Ser. No.09/005,654, filed Jan. 12, 1998, which is a continuation of U.S.application Ser. No. 08/478,181, filed Jun. 7, 1995, which is a divisionof U.S. application Ser. No. 08/344,524, filed Nov. 23, 1994, which inturn is a continuation of U.S. application Ser. No. 08/025,957, filedMar. 3, 1993, which in turn is a continuation-in-part of U.S.application Ser. No. 07/839,911, filed Feb. 21, 1992.

BACKGROUND OF THE INVENTION

[0002] 1. Field of The Invention

[0003] The present invention generally relates to a vascular prosthesis,and more particularly to an intraluminal stent which has a flexible andelastic tubular construction with sufficient hoop strength to preventelastic recoil of balloon-resistant strictures or to produce delayeddilation of those strictures.

[0004] 2. Description of the Prior Art

[0005] The prior art includes a wide variety of intraluminal stents andgrafts. For example, Palmaz U.S. Pat. No. 4,733,665 discloses aballoon-expandable intraluminal graft, including an embodimentcomprising a wire mesh tube. Intersecting wire members, secured to oneanother at their intersections by welding, soldering or gluing, form thewire mesh and define a diamond-like pattern. This structure provides arelatively high resistance to radial collapse; but it suffers a numberof disadvantages. First it is a rigid structure which cannot easilyassume the configuration of a curved vessel which receives it. Secondone must us a balloon catheter to expand and implant it. Thisrequirement limits the length of the graft, as does the rigidity.

[0006] Other prior stents have more flexible constructions; but theysuffer other disadvantages. Wiktor U.S. Pat. No. 4,886,062, for example,discloses a stent which has a relatively flexible construction. Thisconstruction includes a deformable wire bent into a zig-zag design andcoiled in a spiral fashion. The resulting wire tube has an openconfiguration with a reduced hoop strength. Each hoop lies essentiallyisolated from the adjacent hoops and does not obtain substantial supportfrom them. Moreover, the open configuration increases the risk thatplaque elements may herniate through the coil. Finally, one must use aballoon catheter to expand and implant it. Thus, the length of the stentcannot exceed the balloon length of available balloon catheters.

[0007] The intraluminal stent of the present invention avoids thedisadvantages of the prior art stents and grafts. It has sufficient hoopstrength to prevent elastic recoil of balloon-resistant strictures. Thestent of the present invention has a flexible construction which allowsit to follow the curvature of the vessel which receives it. It has anelastic construction which allows implantation without a ballooncatheter. This elasticity further allows compression of the structureand recoil upon implantation to produce delayed dilation of thereceiving vessel.

SUMMARY OF THE INVENTION

[0008] In accordance with an embodiment of the present invention, anintraluminal stent includes a predetermined length of wire having asinuous or zig-zag configuration and defining a continuous helix with aplurality of connected spirals or hoops. A plurality of loop membersconnect adjacent apices of adjacent helix hoops. The stent iscompressible and self-expandable substantially to the configurationprior to compression.

[0009] In accordance with an alternative embodiment of the presentinvention, an intraluminal stent includes the continuous helix and theplurality of loop members described above. It also includes a prostheticgraft disposed longitudinally of the wire helix within its centralopening (or around the wire helix). One or more of the loop memberssecures the graft to the wire helix. This graft is a flexible, tubularshell which allows the wire helix to contract and recoil.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a more complete understanding of this invention one shouldnow refer to the embodiments illustrated in greater detail in theaccompanying drawings and described below by way of examples of theinvention. In the drawings:

[0011]FIG. 1 is a perspective view of the intraluminal stent of thepresent invention;

[0012] FIGS. 2-4 are side elevation view of a suture connection for thestent of FIG. 1;

[0013]FIG. 5 is a sectional view of the devices used to implant thestent of FIG. 1;

[0014]FIG. 6 is a sectional view of the sheath and catheter devices usedto implant the stent, showing the catheter holding the stent in place asthe sheath moves out of the body vessel.

[0015]FIG. 7 is a side elevation view of an alternative embodiment ofthe stent of the present invention;

[0016]FIG. 8 is a sectional view taken along the line 8-8 in FIG. 7;

[0017]FIG. 9 is a partial perspective view of the stent of FIG. 7,showing a suture connection for the stent; and

[0018]FIG. 10 is a perspective view of the mandrel used to form the wirehelix of the present invention.

[0019] While the applicant will describe the invention in connectionwith preferred and alternative embodiments, one should understand thatthe invention is not limited to those embodiments. Furthermore, oneshould understand that the drawings are not necessarily to scale. Incertain instances, the applicant may have omitted details which are notnecessary for an understanding of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0020] Turning now to the drawings, FIG. 1 shows the intraluminal stentof the present invention generally at 10. This stent includes a wirebody 11 made out of a predetermined length of wire having a sinuous orzig-zag configuration and defining a continuous helix with a series ofconnected spirals or hoops. It also includes loop members 12 whichconnect adjacent apices of adjacent helix hoops to help define thetubular stent. The loop members 12 may connect all or some of the pairsof adjacent apices.

[0021] The wire body 11 is an elastic alloy which provides radialelasticity for the stent. Preferably, it is a nitinol alloy which hassuperior elasticity and fatigue resistance. The wire has a roundcross-section; but its cross-section may also be any one of a variety ofshapes, e.g., triangular, rectangular, etc. Alternatively, any materialof sufficient strength and elasticity and the other propertiesidentified above may form the wire body, including stainless steel,tantalum, titanium, or any one of a variety of plastics.

[0022] The loop members 12 connect adjacent apices of adjacent hoops ofthe wire body 11 so that the adjacent apices abut each other (See FIGS.2-4). Thus, each hoop receives support from adjacent hoops, increasingthe hoop strength of the overall stent structure and minimizing the riskof plaque herniation. The loop members 12 are ligatures of suturematerial with the ends tied together to form a loop. This material ispolypropylene material or any other biocompatible material of sufficientstrength. Although sutures are the preferred connecting means, otherconnecting means such as staples and rings made of metal or plastic mayprovide the same function.

[0023] The stent structure of the present invention allows compressionprior to implantation in a human or animal vessel. After implantation,upon release of the compression force, the stent structure recoils (orself-expands) to its original configuration. Thus, it continues toprovide dilating force in the implanted state. The structure providesflexibility which allows the stent to follow the curvature of the vesselwhich receives it.

[0024] Turning now to FIGS. 7-9, an alternative embodiment of thepresent invention includes the wire body and suture connectionsdescribed above. This alternative also includes a prosthetic graft 13disposed inside the central opening of the wire body. The graft 13 is around, open tube made of polytetrafluoroethylene (PTFE), dacron or anyother suitable biocompatible material. One or more hoop members connectthe graft 13 to the wire body 11 as shown in FIG. 9. In place, the graftcloses the diamond shaped openings of the stent structure to furtherminimize plaque herniation and minimize the flow of fluid and cellularelements through the structure.

[0025] Alternatively, graft 13 may lie around the outside of the wirehelix. Furthermore, the graft 13 may be co-extensive with the wirehelix; or it may be shorter than the wire helix. Finally, the graft 13may include a plurality of segments disposed within the wire helix oraround the outside of the helix.

[0026] In one example, the graft 13 is a plain weave fabric constructionmade in a seamless tubular form on conventional equipment, either ashuttle narrow fabric weaving machine or a needle narrow fabric weavingmachine. The tube is of multi filament polyester yarn of 40 denier orless (preferably 20, 30 or 40 denier). The wall thickness of the tube is0.2 μm or less (preferably 0.1 μm); and it has a water permeability ofbetween 50 and 500 ml/cm²/min at 16 kPa (millimeters of water per squarecentimeter per minute at a pressure of 16 kPa). The fabric may be coatedwith a drug substance to reduce permeability, cause localanticoagulation, or reduce cellular infaltration.

[0027] The method of making the stent of the present invention includesbending a predetermined length of wire in a zig-zag fashion between thepins 14 of the mandrel 15 and around the mandrel, thus forming a helix(See FIG. 10). The next step includes removing the helix from themandrel by removing the pins and sliding the helix off the mandrel. Theprocess further includes connecting adjacent apices of adjacent helixhoops. A fabricator makes each connection by placing a ligature ofsuture material (or any other suitable material) around the wiresegments which define two adjacent apices and tying the ends of theligature together to form a loop. In applications in which the wire bodyis nitinol wire, the process includes securing the ends of the wire tothe mandrel and annealing the wire to a predetermined temperature (andthus imparting a thermal memory for the annealing shape) before removingthe helix from the mandrel.

[0028] The method of implanting the stent and graft of the presentinvention includes compressing it and placing it into the central boreof an introducing device 16. The next step includes coupling the device16 with the hub 17 of a sheath 18 which extends to the implantationlocation. The next step involves using a catheter 19 to push thecompressed stent to the predetermined location with the catheter, andthen removing the sheath. The final step involves removal of thecatheter to allow the stent to recoil.

[0029] In applications in which the wire body is a nitinol metal, a userreduces the diameter of the stent by first cooling it, e.g., bysubmerging it in ice water. This cooling places the nitinol in amartensitic phase and facilitates manual reduction of the diameter andinsertion of the stent in the central bore of the device 16. The device16 and the sheath 18 restrain the stent until deployment in apredetermined location. At that location in a subject's body, bodyfluids warm the nitinol and place it in an austenitic phase which is thestable phase of this metal and which corresponds to a fully opened orexpanded configuration of the stent (to its original annealed diameter).

[0030] While the above description and the drawings illustrate oneembodiment and an alternative, one should understand, of course, thatthe invention is not limited to those embodiments. Those skilled in theart to which the invention pertains may make other modifications andother embodiments employing the principals of this invention,particularly upon considering the foregoing teachings. For example, onemay use a deformable material to construct the wire body 11 of the stentand then use a balloon catheter to deploy it. The applicant, therefore,by the appended claims, intends to cover any modifications and otherembodiments which incorporate those features which constitute theessential features of this invention.

What is claimed:
 1. A stent comprising a tubular member having hoopsaligned along the axis of said tubular member, each of said hoopscomprising a series of sinusoidal or zig-zag elements including apicesalternatingly pointing in opposite directions along the axis of thestent with at least one apex of one hoop adjoining an oppositely pointedapex of an adjacent hoop and being connected there by a connectingmember.
 2. A stent according to claim 1, wherein said tubular member ismade from a shape memory alloy.
 3. A stent according to claim 2, whereinsaid shape memory alloy is nitinol.
 4. A stent according to claim 1,wherein said connecting member is a suture material.
 5. A stentaccording to claim 4, wherein said suture material is a polypropylene.6. A stent according to claim 1, wherein some of said apices of one hoopadjoin an oppositely pointed apex of an adjacent hoop and are connectedthereto.
 7. A stent according to claim 1, wherein all said apices of onehoop adjoin oppositely pointed apices of an adjacent hoop and areconnected thereto.
 8. A stent according to claim 1, further comprising atubular graft member secured to said tubular member with at least onesaid connecting member.
 9. A stent according to claim 8, wherein saidgraft member lies within said tubular member.